The overall objective of this project is the identification and characterization of tumor-associated antigens of human colonic tumors. Initially, this will be investigated by using human colonic cancer xenografts established in unconditioned golden hamsters and being continuously propagated in these hosts for the last 9 1/2 years. Methods to be employed in the purification of these antigens will include gel filtration, electrophoresis, ultracentrifugation, affinity chromatography, etc., and the development, where appropriate, of sensitive radioimmunoassays for specific antigens. Of immediate interest is the carcino-embryonic antigen (CEA) originally described by Gold and Freedman and synthesized by our human colonic cancer transplants. Immunological and chemical characterization of CEA purified from these tumors will be undertaken and the findings compared to similar preparations made from tumor specimens obtained directly from human sources. In addition to this work with CEA, the presence of other antigenic substances in these tumors will be explored with a view toward identifying colon-associated or colon-specific, normal or neoplastic markers. The relationship of these antigenic markers of colonic cancer to CEA will be elucidated by immunochemical and immunocytochemical methods.